The altering of hair color is an important area of modern cosmetics. Various bleaching agents with varying bleaching capacity are available on the market for the purpose of lightening the natural hair color or for bleaching. The basic principles of bleaching methods are known to the person skilled in the art and can be researched in relevant monographs by, for example, Kh. Schrader, Grundlagen and Rezepturen der Kosmetika, 2nd edition, 1989, Dr. Alfred Hüthig Verlag, Heidelberg, or W. Umbach (Ed.), Kosmetik, 2nd edition, 1995, Georg Thieme Verlag, Stuttgart, N.Y.
The oxidizing agents contained in bleaching agents have the ability to lighten the hair fiber by means of the oxidative breakdown of the hair's natural pigment, melanin. For a moderate bleaching effect, the use of hydrogen peroxide—preferably with the use of ammonia or other alkalizing agents—is sufficient as an oxidizing agent on its own; for a stronger bleaching effect, a mixture of hydrogen peroxide and peroxodisulfate salts and/or peroxomonosulfate salts is conventionally used. Lightening is, however, also associated with damage to the hair, as not only the natural coloring components of the hair but also the other structural constituents of the hair are damaged by oxidation. Depending on the extent of the damage, it can range from coarse, brittle and tangled hair, through reduced resistance and breaking strength of the hair, to breakage of the hair. Larger amounts of hydrogen peroxide and optionally peroxodisulfates tend to be associated with greater damage to the keratin fiber. Although the bleaching agents hitherto available on the market generally have good lightening capacity, they cannot be regarded as ideal because of the hair damage, long application times and possible skin irritation caused by the high concentrations of oxidizing and alkalizing agents. There is therefore still a need for lightening agents that have a good lightening capacity without at the same time damaging the hair fiber.
Lightening or bleaching agents generally require a basic pH, in particular between pH 8.0 and pH 12. These pH values are necessary to ensure that the external cuticle opens and to allow the active species, in particular hydrogen peroxide, to penetrate into the hair. The basic environment constitutes a further cause of damage to the hair and its structure, however, which likewise gains in importance as the application time increases. The splaying of the external cuticle leads moreover to an unpleasant surface sensitivity of the hair, making it more difficult to comb when wet and dry.
The necessary basic pH value is frequently established using ammonia as the alkalizing agent, as ammonia-containing bleaching agents have additional advantages in terms of lightening capacity. For the user, however, such a lightening agent has the disadvantage that in addition to causing additional damage to the hair, ammonia can also lead to irritation of the eyes or scalp, which can give rise to sensitization or even to allergic reactions. Furthermore, such hair treatment agents have a strong, unpleasant odor, which in the worst-case scenario can also lead to irritation of the nasal mucosa. The production and storage of ammonia-containing lightening agents can moreover be associated with problems in terms of handling ability and stability.
A strengthening of the lightening effect in the bleaching of hair with the aid of a combination of certain acyl pyridinium derivatives and hydrogen peroxide is known from the document WO 2009/135700 A1.
It could not be inferred from the prior art to date that a combination of specific acyl pyridinium derivatives, hydrogen peroxide and specific alkalizing agents not only improves the lightening capacity in comparison to a standard bleach containing hydrogen peroxide, as is already known, but additionally also has an optimal lightening capacity without additional damage to the hair and in particular without additional irritation to the eyes or scalp.
The object of the present invention is to provide an agent which not only lightens the hair more intensely than if hydrogen peroxide is used alone but additionally also has an optimal lightening capacity without additional damage to the hair and in particular without additional irritation to the eyes or scalp. These agents should not have noticeably unpleasant odors, nor should they lead to irritation of the scalp and nasal mucosa.
Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with this background of the invention.